Lake Hillier is a saline lake on the edge of Middle Island, the largest of the islands and islets that make up the Recherche Archipelago in the Goldfields-Esperance region, off the south coast of Western Australia. It is particularly notable for its pink colour. A long and thin shore divides the Southern Ocean from the lake.
The water of the lake is otherwise clear and it causes no harm to the human skin and the Dunaliella salina alga is completely harmless as well. In fact, swimming in the lake’s water is safe and fun but impossible to do for normal tourists as the lake can’t be visited.
The reason of its unique colour is still a topic that is not fully understood by scientists, although most suspect it has to do with the presence of the Dunaliella salina microalgae. The Dunaliella produces carotenoids, a pigment found in carrots as well. But the presence of halophilic bacteria in the salt crusts could be another explanation. A reaction between the salt and the sodium bicarbonate that is found in the water may cause it as well.